The present invention relates to the field of electrical circuits, and more particularly, to the field of circuits for controlling a laser diode, for example, in initiating ordnance.
Initiating a pyrotechnic reaction in an ordnance with an electrical signal requires several steps. First, an electrical energy system provides electrical energy to an initiator to start the reaction. The initiator converts that electric energy to thermal energy which heats the ordnance or pyrotechnic material. When exposed to the thermal energy, the ordnance or pyrotechnic material undergoes a pyrotechnic reaction, and rapidly generates gases and hot particles.
For safe operation, the electrical energy system and the initiator must be designed to protect the ordnance from phenomena like radio frequency (RF) fields, electrostatic discharge (ESD), or lightning that can inadvertently start a reaction. Additionally, to ensure that the initiator is constructed properly, it is desirable to nondestructively test the initiator.
An infrared laser diode converts electrical energy into infrared energy when an electrical current flows through it. This makes an infrared laser diode an interesting candidate for a device to convert an electrical signal to energy for initiating ordnance. Unfortunately, high power infrared laser diodes suitable for initiating ordnance are easily damaged by current spikes, such as those that can occur if the laser diode is not turned on or turned off properly. More critically for ordnance applications, laser diodes are low voltage devices, making them susceptible to inadvertent activation by phenomena like ground fault currents. Laser diodes are also susceptible to RF fields, ESD and lightning. Using conventional circuitry to control a laser diode can damage the laser diode during initiator testing or expose the ordnance to inadvertent ignition. Damage during testing would compromise the ability of the laser diode to operate correctly when the initiator is used with an ordnance. Igniting the ordnance prematurely is clearly undesirable.
To help prevent inadvertent ignition, initiators can be indirectly connected to electrical energy systems by a Radio Frequency Attenuating Coupler (RFAC). This involves placing the initiator inside of a Faraday cage, and transferring power from the electrical energy system to the inside of the Faraday cage by magnetic flux. A transformer within the Faraday cage can convert the magnetic flux into a current that can be used to drive a conventional electrical initiator or, via electronic circuits, a laser diode or other device. However, this method of transferring power has substantial losses.